Biocontrol potential of native Algerian bacteria isolated from greenhouses against Botrytis cinerea and Oidium neolycopersici on tomato

Botrytis cinerea and Oidium neolycopersici represent two of the key fungal pathogens of tomato. In this study, 142 isolates were screened for their biocontrol potential against these pathogens. They were initially isolated from rhizospheric and from non-rhizospheric soil samples collected near healthy tomato plants grown in unheated greenhouses showing severe epidemics of grey mould in the Jijel region of Algeria. All the isolates were tested in vitro against B. cinerea using dual culture assays, and a subsample of 40 isolates (20 rhizospheric isolates and 20 non-rhizospheric isolates) was retained. The antagonistic effect of these candidates on spore germination of B. cinerea and their effect against O. neolycopersici and B. cinerea on tomato plants were then evaluated. The dual culture assays showed that non-rhizospheric bacteria were significantly more effective than rhizospheric bacteria in inhibiting the mycelial growth of B. cinerea. In planta, however, rhizospheric isolates showed significantly higher protective levels. This protective effect was significantly correlated to the ability of bacterial isolates to inhibit spore germination of B. cinerea. Taken together, these results allowed us to retain seven isolates with over 90% of efficacy against B. cinerea. These isolates were also able to protect tomato plants against O. neolycopersici, and they were identified as, P. argentinensis (SJ2), Serratia marcescens (SJ11), Pseudomonas lactis (SJ55), Pseudomonas veronii (RSAB3), Stenotrophomonas maltophilia (RTB17), Bacillus subtilis (SA14) and Bacillus toyonensis (SA87). This study showed promising results that could be exploited for a potential application of bacterial-based biocontrol agents efficient against both B. cinerea and O. neolycopersici.